Dual range manual preset timer

ABSTRACT

A dual range manual preset timer drives through the first part of its timing range at relatively high speed to give short timings of relatively high accuracy. It drives through the second part of its timing range to low speed to give long timings where high accuracy is not required. The low speed timing gears are always in mesh to insure against hang up. The high speed gear engages at the change over point in the timing range and drives from this point to the off position. A one way drive on the low speed timing gears permits the faster rotation by the high speed gears.

United States Patent Harris Appl. No.2 192,171

US. Cl ..74/3.52, 200/38 FA Int. Cl. ..G05g 21/00 Field of Search ..74/3.5, 3.52, 3.54;

References Cited UNITED STATES PATENTS 2/1963 Laviana et al. ..74/3.52

[ June 5,1973

3,180,157 4/1965 Harris ..74/3.52

Primary Examiner-Milton Kaufman [57] ABSTRACT A dual range manual preset timer drives through the first part of its timing range at relatively high speed to give short timings of relatively high accuracy. It drives through the second part of its timing range to low speed to give long timings where high accuracy is not required. The low speed timing gears are always in mesh to insure against hang up. The high speed gear engages at the-change over point in the timing range and drives from this point to the off position. A one way drive on the low speed timing gears permits the faster rotation by the high speed gears.

2 Claims, 5 Drawing Figures PATENTEU 5 7 3. 736. 799

IIIJI IIIJI swn'cu CAM GEAR SH\FT cm DRIVEL 24 6 2a 34 45 30 LOW s ew men P\N ION SPEED PINION DUAL RANGE MANUAL PRESET TIMER BACKGROUND OF THE INVENTION This invention relates to timing devices of the manual preset two speed type.

In commercial pressure cookers and similar equipment it is necessary to cook different items for different lengths of time. Certain items require minutes or less and other items need timings up to an hour. In a normal 60 minute timer, the setting error by the user can be up to 1 minute. This is not serious on the long timings. However, on short timings such as 5 minutes, this error is a large portion of the totaltiming and causes substantial variations in results.

To make a single timer usuable for both short and long timings dual range timers have been proposed. In this type of timer the first half of the dual scale can be for example minutes and the second half 45 minutes giving an overall range of 60 minutes. At the midpoint on the scale the timer changes speed. This arrangement makes it possible to set sho'rtaccurate timings and still obtain long timings of suitable accuracy.

BRIEF SUMMARY OF INVENTION The primary object of this invention is the provision of a two speed timing device which is low in cost, reliable in operation and which is suitable for. commercial use.

Anotherobject is the provision of a dual speed timer of the type which runs at low speed for one portion of its dual range and automatically shiftsto high speed for another portion of the dual range, with a speed change mechanism which is simple and which cannot hang up at the speed change point.

The timer embodying the invention is provided with a manual set shift driven by a low speed gear train and a high speed gear train. The low speed gearing remains constantly in mesh and drives the shaft through a one way clutch or ratchotin g mechanism. This provides a positive drive at all times, but permits the shaft to be rotated faster than driven by the low speed gear. Thehigh speed gearing is disengaged when the shaft is manually moved into the low speed dual range, and is reengaged when the shaft is driven to the speed change point. This disengaging and reengaging is performed by a lost motion cam in the shaftwhich withdraws a high speed pinion from the drive gear for the shaft. Manual setting of the shaft without wearing thegears is provided by a friction drive located on the shaftside of all the gearing.

Other objects of the invention will appear from the following description and appended claims.

BRIEF DESCRIPTION OF DRAWINGS DETAILED DESCRIPTION OF INVENTION Reference character 1 indicates a cam shaft extending between the front plate 2 and back plate 3 of an enclosure including a switch panel 4. This cam shaft carries a'main switch cam 5 having a notch 6 and actuating a cam follower 7 supported on shaft 8 extending between plates 2 and 3. This cam follower has a downwardly depending portion 9 which rides the cam and a switch operating portion 10 arranged to engage a switch blade 11 which is mounted on a bracket 12 carried by panel 4. The switch blade 11 also carries a contact 12 who co-operating with the contact 13 carried by blade 14 which is mounted on a bracket 15 secured to panel 4. The blade 11 is biased downwardly thus causing contacts 12 and 13 to be disengaged when the depending portion 9 of the follower is in the cam notch 6 as shown in FIG. 1. This is the off position of the cam.

The cam shaft 1 also carries a cam driver 16 which is mounted on the shaft forwardly of the switch cam 5. Mounted on the cam shaft behind the switch cam 5 is a gear shift cam 17. Cam shaft 1 is driven by a gear 18 through a slip friction drive including a tension washer 19 and a retainer 20. The cam driver 16 is rigidly mounted on shaft 1 while the cams 5 and 17 are loosely mounted on the shaft and supported between the driver 16 and the tension washer 19. As shown more clearly in FIG. 4, camS is provided with an opening 22 and cam 17 is provided with a slot 23. A drive pin 24 is secured to the cam driver 16 and extends through opening 22 andslot 23. This provides a lost motion drive between the cam shaft 1 and the switch cam and gear shift cams and 17 respectively.

The back plate 3 carries a timer motor 25 having a pinion 26 meshing with a gear and pinion 27. The gear and pinion 27 is carried by a shaft 28 which is freely supported between the back plate 3 and front plate 2. This shaft also carries a bearing 29 supporting the gear shift cam follower 30 whichcarries an idler gear 31 meshing with the pinion portion'of the gear and pinion 27. As shown more clearly in FIG. 4, the gear shift cam follower 30 includes a depending portion 32 which rides the cam 17. Cam 17 is formed with a relatively high surface 33 and a low surface 34 joined by inclined camming surfaces 35 and 36. The cam follower 30 is biased against cam 17 by means of a torsion spring 38 one end of which bears on an intumed portion 40 of cam follower 30, the other end being supported on a suitable stationary support. When the cam shaft 1 is positioned so that the high portion 33 of the cam 17 is an engagement with the follower portion 32 of the'cam follower, the idler gear 31 carried by the cam follower is disengaged from gear 18. However, when the shaft is positioned so that the low portion 34 of the cam is adjacent the cam follower, the idler gear 31 is urged into engagementwith gear 18 by the biasing spring 38.

The shaft 28 at its front end carries a pinion 42. The gear and pinion 27 and pinion 42 are splined to' shaft 28 so that the gear 27 drives the pinion 42. The cam follower bearing 29 is loose on the shaft thus allowing the shaft to be turned by the timer motor without affecting the position of the cam follower 30. The pinion 42 drives a gear 43 carried by a pinion shaft 44 extending freely between the timer plates 2 and 3. Shaft 44 at its back end carries a pinion 45 meshing with the drive gear 18 for the cam shaft. The back end of shaft 44 fits into a slot 46 in back plate 3, this slot being arranged at an angle of approximately 45 to the motion of gear 18 at the point of engagement with the pinion 45. The pinion shaft 44 is urged upwardly as seen in FIG. 1 and toward engagement of the pinion with the gear by means of a spring 47 supported on stud 48 mounted on one of the plates.

OPERATION FIG. 1 shows the timer in the off position in which the switch cam 5 is located with its notch 6 below the depending portion 9 of cam follower 7, thus causing the switch contacts 12 and 13 to be disengaged. Also in this off position, the cam follower portion 32 of lever 30 is in its down position on cam 17 causing the idler pinion 31 to be engaged with the main drive gear 18. If the user desires a relatively long timing period such as 30 I minutes he turns the knob 50 to the point marked 30 on the dial 51. (FIG. 5) If the knob is turned clockwise from the off position, the cam follower 7 is first raised out of the notch 6 on cam'S causing the contacts to engage as shown in FIG. 2. When the knob is turned past the 5 minute point on the dial, the cam surface 36 on cam 17 lifts the cam follower 30 and disengages the idler gear 31 from the main gear 18. The idler gear at this time is driven by the gear 27 but performs no function due to its being disengaged with gear 18.

The timer motor 25 now operates to drive pinion 42 which in turn drives pinion 45 through gear 43. Pinion 45 is driven in a clockwise direction as seen in FIG. 1 and this drives the cam shaft 1 in a counter-clockwise direction back toward the off position on the dial. At this time the reaction on pinion 45 in driving gear 18 is such as to cause the pinion to pull into the gear and thus provides a positive drive. The cam shaft assembly is now driven at slow speed back to the gear shift portion of the dial which in this case is the 5 minute point. This point is illustrated in the FIG. 2 where the cam follower 30 is just ready to ride off the upper level 33 of the gear shift cam 17. When this occurs the cam follower rides down the sloping portion 36 of the cam with rapid action as the cam 17 is free to advance due to the lost motion drive provided by pin 24 and slot 23. This motion of the cam follower 30 brings the pinion 31 into engagement with gear 18. This in effect short circuits the gear. reduction provided by pinion 42 and gear 43 and causes the cam shaft 1 to be driven at high speed through the high speed range of the dial and back to the off position. When the cam reaches the off position the switch cam follower 7 drops into the notch 6 of switch cam 5. This cam advances rapidly due to the lost motion drive and allows opening of the contacts 12 and 13 with rapid action.

During the high speed portion of the timing range, the low speed pinion is prevented from interfering with the high speed roation by the arrangement of the slot 46 and the biasing spring 47. The high speed movement of gear 18 in effect cams the pinion 45 away from the gear thus allowing gear 8 to rotate freely.

From the foreging it will be apparent that the inven-' tion provides a dual range manual preset timer in which the timer is driven at slow speed through part of its range and then shift gears to drive at high speed during the latter part of the range. It will be further apparent that the low speed driving mechanism is never diasabled which insures that the timer will always drive into the high speed range even though the gear shift mechanism should malfunction. It will also be apparent that the manual presetting of the timer shaft is permitted by the slip friction drive between the shaft and its final drive gear. This is independent of the speed change gearing. The slip friction drive takes the wear of manual presetting making setting easy and providing for long life of the timer.

It should be noted that cams 5 and 33 are symetrical in the notch arrangement, thus permitting rotation of the timer knob in either direction from the off position in order to start a timing period.

I claim:

1. In a dual range manual preset timing mechanism, the combination of, a control device, a timing shaft, means for actuating said control device from one position to another when the timing shaft is moved to a predetermined position and for actuating the control device back to the first position when the timing shaft is moved away from said predetermind position, drive means including a slow speed timing mechanism and a motor for driving said timing shaft in one direction towards said predetermined position, said slow speed mechanism including one way drive means providing a positive drive for said shaft in said one direction at all times while allowing free movement of said shaft in said one direction at a rate faster than caused by the slow speed mechanism, means including a high speed drive mechanism driven by said motor for also driving said shaft in said' one direction and at a speed higher then caused by the slow speed drive mechanism, slip friction drive means associated the said shaft for allowing manual setting movement thereof in either direction irrespective of both the high speed and low speed drive means, means for disengaging the highspeed drive means when the shaft is turned manually from a high speed timing range into a low speed timing reange, and for reengaging said high speed drive means when the low speed drive means drives the cam shaft back to the low speed timing range.

2. The combination recited in claim 1 in which the means for disengaging the high speed drive means and the means for reengaging the same includes a lost motion cam carried by the timing shaft and a cam follower riding the cam and controlling the high speed drive means. 

1. In a dual range manual preset timing mechanism, the combination of, a control device, a timing shaft, means for actuating said control device from one position to another when the timing shaft is moved to a predetermined position and for actuating the control device back to the first position when the timing shaft is moved away from said predetermind position, drive means including a slow speed timing mechanism and a motor for driving said timing shaft in one direction towards said predetermined position, said slow speed mechanism including one way drive means providing a positive drive for said shaft in said one direction at all times while allowing free movement of said shaft in said one direction at a rate faster than caused by the slow speed mechanism, means including a high speed drive mechanism driven by said motor for also driving said shaft in said one direction and at a speed higher then caused by the slow speed drive mechanism, slip friction drive means associated the said shaft for allowing manual setting movement thereof in either direction irrespective of both the high speed and low speed drive means, means for disengaging the high speed drive means when the shaft is turned manually from a high speed timing range into a low speed timing reange, and for reengaging said high speed drive means when the low speed drive means drives the cam shaft back to the low speed timing range.
 2. The combination recited in claim 1 in which the means for disengaging the high speed drive means and the means for reengaging the same includes a lost motion cam carried by the timing shaft and a cam follower riding the cam and controlling the high speed drive means. 